The proposed project will combine basic science imaging research with a prospective clinical trial to examine whether stereotactic breast needle biopsy (SBNB), guided by electronic Imaging, can be used to diagnose and manage patients with nonpalpable breast abnormalities. We have developed a digital stereotactic mammography system that uses a charge-coupled device (CCD) as the image receptor. This system generates high resolution digital breast images in 3-5 seconds, allowing the position of a biopsy needle to be rapidly verified. Thus, the accuracy and efficiency of performing percutaneous biopsy of nonpalpable breast lesions will be enhanced. The digital imaging system is now assembled and we currently are performing basic science experiments to assess the fundamental characteristics of the system, including modulation transfer function, signal to noise ratio, photon fluence, radiation dose and detective quantum efficiency. Next, the system will be used clinically to perform SBNB on 400 patients with nonpalpable breast lesions. Surgery will be performed only on those patients with a SBNB that is positive for cancer. Patients with negative SBNBs will be managed conservatively. and closely followed with mammography and physical examination every six months for two years. Any change in the lesion will prompt re-evaluation by needle or surgical biopsy. After two years of close follow-up, patients will return to routine breast cancer surveillance. Finally, we will evaluate the cost effectiveness of SBNB as a substitute for surgical breast biopsy in the evaluation and management of breast disease.